As I recall a story in a 1970's issue of the "Restorer", this coupe was a prototype that made it into the public. In the 1950's, a Model A lover saw this car parked on a Los Angeles street and took photos of it because it was so unusual. Not much was known about it at the time and everyone assumed that as a prototype, it had been destroyed by Ford. But it hadn't been. It had at least 25 years use by who-knows-how-many owners by the time the photos were taken, which were printed in the article. One could clearly see 1950's cars parked in front and behind the coupe, so that sets the timeframe as being reliable. Was there more than one of these three-window prototypes?
I know that the 1929 Cabriolet prototype also escaped Ford's destruction boys after its New York Car Show debut. Larry and Gwen Machek in Texas have the remains of the body, which has a couple distinctive identifying features that didn't make it into production 1929 Cabriolets.
Marshall